There have been various proposals in the past as to the design of an orbiting space station. Initially space stations were designed that could be lifted into earth orbit in one shot, and then deployed out to their operational form. The generally toroidal space stations described in U.S. Pat. No. 3,144,219 and No. 3,169,725 are classic examples of this approach. The more recent Skylab is an actual example of such a one-shot space station that was put into earth orbit. Shortcomings of the one-shot system are in the severe size and weight restrictions that are placed on the space station. It must be light enough and small enough to be placed in orbit by a single rocket launch. These size and weight restrictions certainly limit not only the effective working life of a space station, due to the limit placed on exhaustible staples such as foodstuffs, respiration, energy and thrust-generating chemicals, but they also place a limit on such intangible necessities as an artificial gravitational field which will be necessary to avert any physical deterioration that can be initiated by extended periods of weightlessness. Due to its booster-sized cylindrical shape, Skylab was not intended to induce an artificial gravitational field on its inhabitants; though both toroidal space stations were designed to produce an artificial gravitational field through simple rotation, the rate of rotation would be rapid, on account of their rather short diameters. Each toroidal station would also have to rely on a rather complicated packaged structure that would have to be either inflated or mechanically erected once reaching orbit. Gas leakage, by way of micro-meteorite impacts to the inflatible sections and improperly seated gaskets and seals between the mechanically joined section that could not be corrected without disengaging all of the sections at one time, is also a potential problem.
At the other end of the design spectrum is the space station, or vehicle, which is entirely self-sufficient in supporting many forms of terrestrial life. These structures are quite large -- so large that it may not be possible for them to be fabricated piecemeal on earth and then lifted, bit by bit, into earth orbit. It has been suggested, in fact, that they may have to be fabricated and assembled in orbit, with raw materials from earth's moon or the transmartian asteroid belt. These pressure tight structures, as represented in U.S. Pat. No. 3,749,332, are of generally cylindrical shape with at least one dome-like end. Gravity-like centrifugal forces are generated on the interior arcuate surface of the structure by simple rotation. It is on this interior surface where terrestrial life, both plant and animal, is cultivated and used to sustain the structure's human life using provisions of plant supporting lunar soil, atmospheric gases and water, as well as ample sunlight made available through one or more transparent surfaces. It is speculated that a number of these large structures, located at either lagrangian point L4 or L5 of the earth-moon orbital system, could become sites of significant terrestrial colonization, as well as ports from which deep space exploration could be conducted.
It would be a gross understatement to consider the building of such large structures anything less than heroic. The logistics of such a construction project would imply the existence of a permanent earth colony on the moon's surface -- if the raw materials to be used in the shell construction were to be extraterrestrial. Regardless of the origin of the raw materials, at least one orbiting space station will have to be in a position to provide living quarters for the construction workers, and serve as the assembly point for both the materials and the large structure itself. Fortunately, the presence of an operational space shuttle will make the consideration of any one-shot space station system unnecessary in any such endeavor.